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Advances in Environmental Biology

Journal home page: http://www.aensiweb.com/AEB/

Corresponding Author: Aidah Jumahat, Faculty of Mechanical Engineering,Universiti Teknologi MARA(UiTM), 40450, Shah Alam, Selangor Darul Ehsan, Malaysia,

+60355435135, E-mail: norhashidah.manap@gmail.com

Tensile And Compressive Properties Of Glass Reinforcement In Kenaf Reinforced Epoxy Composite

Norhashidah Manap, Aidah Jumahat, A.Ludin

1Faculty of Mechanical Engineering, Universiti Teknologi MARA, 40450 Shah Alam, Selangor Darul Ehsan, Malaysia.

A R T I C L E I N F O A B S T R A C T

Article history:

Received 28 February 2014 Received in revised form 25 May 2014 Accepted 6 June 2014

Available online 20 June 2014

Keywords:

Kenaf fibre Glass fibre Longitudinal fibre direction Transverse fibre direction

Background: Natural fibres are getting attention from researcher to be reinforced in polymer composites; as the trend to produce greener product is emerging rapidly. Apart from that, natural fibres also possess good mechanical properties; low cost and safer handling compared to synthetics fibres. However, polar behaviour of natural fibres has become a challenge for natural fibres to be used in polymer composites since it will lead to poor interfacial adhesion. This property will cause poor mechanical properties of overall composites. Many researches has been done to overcome the issue for example by chemically and physically treated the fibres to improve the adhesion between matrix and fibre. Hybridization is also one of the methods to improve mechanical properties of overall composites. This is done by hybridizing the synthetic fibre which exhibit good bonding with the matrix and high mechanical strength with natural fibres. Glass fibre has been used in this experiment where the plain woven glass has been lay-up at the outer layer of the natural fibre whereas the kenaf has been wound in longitudinal and transverse direction. The composites are the vacuum-bagged before tested for tensile and compressive test. Objective: The aim of this experiment is to study the effects of hybridization of kenaf and glass in epoxy composites in longitudinal and transverse kenaf direction in terms of tensile and compressive properties using ASTM standard D3039M and D3410M respectively. Results: It is shown that, the hybrid composites, shows significant result to improve the tensile strength of natural fibre by increasing value of 62% and 240% both for longitudinal and transverse kenaf direction respectively. While increasing value of 25% and 275% for tensile modulus. It is proven that incorporation of glass fibre in natural fibre composites enhance the mechanical properties of resultant composites. Conclusion: Incorporation of glass fibre in kenaf composite shows positive result in tensile and compressive properties. Longitudinal direction of kenaf fibre shows higher tensile and compressive properties compared with transverse kenaf direction.

© 2014 AENSI Publisher All rights reserved.

To Cite This Article: Norhashidah Manap, Aidah Jumahat, A.Ludin., Tensile And Compressive Properties Of Glass Reinforcement In Kenaf Reinforced Epoxy Composite. J. Appl. Sci. & Agric., 8(8), 2673-2681, 2014

INTRODUCTION

Fibre reinforced polymer (FRP) is a composite material consisting of a polymer matrix embedded with high-strength fibres, such as glass, aramid and carbon. Generally, polymer can be classified into two classes, thermoplastics and thermosettings. Thermoplastic materials currently dominate, as matrices for bio-fibres; the most commonly used thermoplastics for this purpose are polypropylene (PP), polyethylene, and polyvinyl chloride (PVC); while phenolic, epoxy and polyester resins are the most commonly used thermosetting matrices.

In the recent decades, natural fibres have become an alternative reinforcement in polymer composites which attracted the attention of many researchers and scientists due to their advantages over conventional glass and carbon fibres. Natural fibre is a renewable and low priced natural resource. Polymers reinforced with these fibres are relatively new class of material with good economic and ecological outlooks [1,3]. They also exhibit relatively good overall mechanical behaviour with low oversensitivity; the possibility to recycle natural fibre composites by combustion as well as the fact that the fibres are re-growing resource is another promising feature of this kind of fibre. Due to these attractive features, natural fibre has getting interest to be used as fibre in polymer composites in structural and non-structural application. [2].

Natural fibres are subdivided based on their origins i.e., whether they are derived from plants, animals, or

minerals. According to previous studies, plant fibres are the most popular of the natural fibres, used as

reinforcement in fibre reinforced composites. Plant fibres include bast fibres, leaf or hard fibres, seed, fruit,

wood, cereal straw, and other grass fibres. While natural fibres have many advantages, they also exhibit certain

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disadvantages which include high moisture absorption and low interfacial adhesion between the fibre and the matrix due to polar behaviour of hydroxyl group in natural fibre and non-polar behaviour of the matrix. This may lead to poor mechanical properties of the resultant composites.

Glass fibre is one of mostly used synthetic fibre in polymer composites. It is a low cost and fairly good in mechanical properties which make the fibre suitable for non-critical structural usage such as automotive industries where cost and production is an important factor. Glass fibre is also one of the widely used fibre to be hybridized with other synthetic fibres to lower the overall cost.

Other than that, glass fibre is among of the popular composites to be compared and hybrid with natural fibre. This is due to the fact that the specific properties of them are comparable and the natural fibre has the opportunity to replace glass fibre [12,11]. In terms of strength glass fibre possess higher mechanical strength compared to natural fibre and relatively higher cost of production [2].

One of the methods to improve the mechanical properties of the natural fibre composite is by hybridizing it with synthetics fibre. ( i.e.: glass, carbon, aramid fibre) [4]. Hybridization can give positive and negative effects of overall composites performance. The function of hybridization is to combine the properties of such fibres used in composites [13].

In this experiment, the tensile and compressive properties of the kenaf reinforced polymer, plain woven glass/kenaf reinforced polymer composites (longitudinal and transverse kenaf direction) and plain woven glass reinforced polymer were investigated.

Tensile test is a common mechanical test to determine the strength of materials. In longitudinal tensile loading, tensile strength of composites is mostly depending on mechanical properties of the fibre and how much of load the matrix can transfer to the fibre which depends on the interfacial bond between the fibre and the matrix. This direction of fibre alignment usually shows the highest tensile strength [7].

The transverse strength is governed by many factors which include the properties of the fibre and matrix, the interface bond strength, the presence and distribution of voids, and the internal stress and strain distribution.

The most prominent feature of the transverse strength is that for FRP it is usually less than the strength of the parent resin [5,6]. The transverse tensile strength of a unidirectional composite in which there is little or no interface bonding is determined by the strength of the resin. When the fibres are strongly bonded to the matrix, the transverse strength is dependent on interface strength as well as the strength of the matrix.

The material has to provide lateral support and stability for usage. The matrix is one of crucial factor in compressive properties of composite materials. In polymer matrix in which the matrix modulus is relatively low compared with the fibre modulus, failure in longitudinal compression is often initiated by localized buckling of fibres [8]. Depending on whether the matrix behaves in an elastic manner or shows plastic deformation, two different localized buckling modes are observed: elastic microbuckling and fibre kinking [9]. Other failure modes have also been observed in longitudinal compressive loading of unidirectional continuous fibre- reinforced composites which include shear failure of the composite, compressive failure or yielding of the reinforcement, longitudinal splitting the matrix, matrix yielding, interfacial debonding and fibre splitting.

In transverse compressive loading, the failure is initiated by fibre-matrix debonding. The transverse compressive modulus and strength are considerably lower than longitudinal compressive modulus and strength.

The transverse compressive strength is found nearly independent of fibre volume fraction.

The advantage of using woven fabric laminates is that they provide properties that are more balanced in longitudinal/transverse directions than unidirectional laminates. Although multilayered laminates can also be designed to produce balanced properties, the fabrication time for woven fabric laminates is less than that of a multilayered laminate. However, the tensile strength and modulus of a woven fabric laminate are, in general lower than those of multilayered laminates. The principal reason for their lower tensile properties is the presence of the fibre undulation in woven fabrics as the fibre yarns in the fill direction cross over and under the fibre yarns in the warp direction to create an interlocked structure. Under tensile loading, these crimped fibres tend to straighten out, which creates high stresses in the matrix. As a result, microcracks are formed in the matrix at relatively low loads. Another factor to be considered is that the fibres in woven fabrics are subjected to additional mechanical handling during the weaving process which tends to reduce their tensile strength.

Methodology:

Sample preparation:

Materials:

Materials used in this experiment were intertwined untreated long fibre kenaf bast supplied by Innovative Pultrusion Sdn.Bhd. Plain woven glass supplied by local company and epoxy resin (Morcrete BJC 39) supplied by Morstrong Industries Sdn.Bhd.

Dry Filament winding method:

Lab scale of dry filament winding machine is used in this experiment with varying of longitudinal and

transverse fibre alignment.Dry filament winding is a process to produce continuous fibre length. It can produce

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a clean process but not as flexible and cheaper as wet filament winding. In this experiment, an average of 1.2mm diameter intertwined long bast kenaf is filament wounded on rectangular aluminum frame (frame RPM:

19 rpm; Fibre Guider: 12 rpm).

Fig. 2.1: Lab- scale filament winding machine

Vacuum bagging method:

Figure 2.3 shows the schematic diagram of a bag-moulding process. The bag-molding method is used predominantly in the aerospace industry where high production rate is not an important consideration [10]. In this process the pressure is applied to squeeze out excess resin before the gel point is reached at any location since rich resin region may create weak interlaminar layers in the laminate. In this experiment, the wounded kenaf was impregnated with morcrete BJC 39 epoxy with amine hardener in 3.7:1.4 ratios. The impregnated composite was then vacuum-bagged for 1 hour before being left for 24 hours at room temperature for curing process to produce kenaf fibre reinforced polymer (KFRP).Hybrid glass/kenaf fibre as shown in figure 2.3, was fabricated where the plain weave glass has been used as face-sheet of the wounded kenaf using hand lay-up method before impregnated with epoxy and vacuum bagged. Hand lay- up method was used to fabricate plain weave glass before impregnated with using epoxy and vacuum bagged to produce glass fibre reinforced polymer.

Fig. 2.2: Schematic diagrams of vacuum bagging system

Fig. 2.3: Hybrid glass/kenaf composite lay-up

Mechanical test:

Tensile and compressive test were conducted according to ASTM 3039/3039M-08 and ASTM

D3410M/D3410M-03(Reapproved 2008) respectively using variables of kenaf fibre direction of longitudinal

and transverse to determine the composite strength. The tensile test and compression test were performed using

Instron 3382 100kN Floor Model Universal Testing Systems

using speed rate of 2mm/min and 1.5mm /min

respectively. The specimen size used as per stated in Table 2.1 and 2.2.

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Fig. 2.4: Instron 3382 100kN Floor Model Universal Testing Systems

Table 2.1: Specimen size used in tensile test specimen size

Tensile test

overall length (mm)

width (mm)

thickness (mm) Kenaf-FRP and Glass/Kenaf-FRP (longitudinal kenaf direction) 250 15 ≈4 Kenaf-FRP and Glass/Kenaf-FRP (transverse kenaf direction) 175 25 ≈4

Glass - FRP 250 25 2.5

Table 2.2: Specimen size used in compressive test specimen size

Compressive test

overall length (mm)

width (mm)

thickness (mm) Kenaf-FRP and Glass/Kenaf-FRP (longitudinal kenaf direction) 140 10 ≈4 Kenaf-FRP and Glass/Kenaf-FRP (transverse kenaf direction) 140 25 ≈4

Glass - FRP 140 25 2.5

2.4 Physical Test:

Physical tests include density and optical microscopic test were done to determine the density and failure analysis of the composites.

2.4.1 Optical Microscope test:

Optical microscope is one of the methods of fractographic study. It is usually used to determine the cause of failure. In this experiment, the tensile and compressive failures were viewed using optical microscope using 10X magnification.

2.4.2 Density test:

Density test in this experiment is using the Archimedes theory where the weight of materials in water and air were taken and calculated to determine the density.

RESULTS AND DISCUSSION

3.1 Tensile properties of composites:

The failure mechanism could be distinguishable in uniaxial tensile test which is fracture at the gauge length right at the middle of the sample at the lateral. Composites are known for their anisotropic behavior where the strength depends on the direction of the fibre. Theoretically, longitudinal fibre alignment will produce the strongest attributes for tensile test as normally the fibre which usually is stiffer than matrix will bear the load applied as long as the volume fraction of the fibre of the fibre is sufficient for the composite as the load bearer.

However, for transverse loading fibre direction, the strength predicted to be the lowest as the fibre will act as the

hard inclusion in the matrix instead of the principal load-carrying member. The experimental results have

confirmed the theory where the increasing of approximately 847% of tensile strength for kenaf/epoxy laminates

and 350% for hybrid of plain woven/kenaf laminates both for longitudinal and transverse direction of kenaf as

shown the figure 3.1.

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Fig. 3.1: Graphs of tensile properties of experimental composites

Hybridizing of glass fibre as face-sheet in the kenaf laminates also proven to increase the tensile properties of the natural fibre apart from protecting the fibre from humidity. The tensile modulus of composites also proven to be influenced by fibre direction and hybridization of synthetics fibre in the laminates by increment of tensile modulus in transverse direction and hybridizing the natural fibre with glass fibre as per shown in the graph above. It is shown that the increment of 667% of tensile modulus for longitudinal direction of kenaf fibre composite compared to transverse direction. The tensile modulus of hybridization glass fibre with longitudinal direction of kenaf fibre also showed increment of 24% and 275% for transverse kenaf fibre direction. Specific properties of the composites shown insignificant result since the density measured using Archimedes method for all composites is approximately the same as per data in table 3.1.

Table 3.1: Density of experimental composites

SAMPLE Weight on air, A

( g )

Weight on Liquid, B ( g )

Density,

( )

GKFRP 0.3998 0.0949 1.2045

KFRP 0.4659 0.0946 1.1526

GFRP 0.3497 0.0947 1.2596

Compressive properties of composite:

The graphs in figure 3.2 show the value of compressive properties of the composites. It is shown that

compressive strength for longitudinal and transverse direction of pure kenaf composites are approximately the

same value. This is may cause by the interfacial debonding of natural fibre with the matrix for longitudinal

kenaf direction composites as per shown in figure 3.8. It is shown that the incorporation of glass fibre in natural

composite improve the compressive strength and modulus of both longitudinal and transverse kenaf fibre

direction.

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Fig. 3.2: Graphs of compressive properties of the experimental composites

Tensile vs. compressive strength of composites:

From the graph shown in figure 3.3, we can conclude that the tensile strength for longitudinal kenaf, longitudinal hybrid kenaf/plain woven glass and plain woven glass composites are higher than its compressive strength. However, for transverse kenaf composite, the tensile strength is lower than compressive strength .This is due to the fact that in transverse direction of fibre, the fibre gives negatives effect on the strength. It strength obtained usually are lower than the strength of the matrix. Hybridization of plain woven glass in natural fibre change the pattern where the tensile strength is slightly higher than compressive strength by 12%.The same phenomenon occur in plain woven glass laminates where the tensile strength is higher than compressive strength.

Fig. 3.3: Graphs of tensile strength versus compressive strength for experimental composites

Physical test:

Optical microscope:

Tensile failure of composites:

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Fig. 3.4: Tensile failure of longitudinal kenaf composites

Fig. 3.5: Tensile failure of transverse kenaf composites

Figure 3.4 above shows the tensile failure of longitudinal kenaf fibre alignment for pure kenaf and hybrid laminates. It can be seen that the kenaf fibre pullout in a broom-like fracture showing the low interfacial adhesion between fibre and the brittle matrix. While for transverse direction of kenaf fibre composites in Figure 3.5, the composite fracture at fibre-matrix interfacial indicates that poor bonding between fibre and matrix.

Fig. 3.6: Tensile failure of glass/kenaf composites for longitudinal kenaf direction

Fig. 3.7: Tensile failure of glass/kenaf composites for transverse kenaf direction

Figure 3.6 shows the tensile failure of hybrid glass/kenaf composite in longitudinal kenaf direction and Figure 3.7 shows tensile failure of hybrid glass/kenaf in transverse kenaf direction .The failure of kenaf fibre in both composites show the same characteristic of failures as before (refer Figure 3.4 and 3.5 respectively).The tensile failure of glass fibre shows that the breakage of weft direction of glass with minor elongation.

Compressive failure of composites:

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Fig. 3.8: Compressive failure of longitudinal kenaf composites

Fig. 3.9: Compressive failure of transverse kenaf composites

The figure above shows the compressive failure of longitudinal kenaf fibre alignment composite structure where interfacial debonding between matrix (matrix crack in perpendicular direction due to compressive load applied) and the natural fibre as the fibre were still intact in the composite. For transverse natural fibre direction, the compressive load lead to the matrix crack as shown in figure 3.7.

Fig. 3.10: Compressive failure of glass/kenaf composites for longitudinal kenaf direction

Fig. 3.11: Compressive failure of glass/kenaf composites for transverse kenaf direction

Figure 3.10 shows the compressive failure of glass/kenaf composites for longitudinal direction.

Incorporation of glass fibre in kenaf composites caused the composites to bend at sharper angle compared to kenaf composites alone. Figure 3.11 shows that the composites totally fail at fibre-matrix interface for transverse direction.

Conclusion:

Natural fibre is a promising fibre in composites industry and many experiments have been done to

overcome their weaknesses and one of them is by incorporating synthetics fibre .In this experiment, we can

conclude that, the hybridization of glass fibre in kenaf composites give positive effects which help to enhance

tensile and compressive properties of natural fibre to be used in various application. Longitudinal kenaf

direction in composites shows higher strength compared to transverse kenaf direction. Glass fiber composites

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show the highest strength followed by hybrid glass/kenaf composites and kenaf composites respectively.

Transverse kenaf direction in composites shows that the fracture at the interfacial of fibre-matrix interfacial showing that weak interfacial adhesion between fibre and matrix in both tensile and compressive test.

ACKNOWLEDGMENT

The authors would like to thank Experiment Management Institute (RMI) UiTM and Ministry of Higher Education Malaysia for the financial supports. The experiment is conducted at the Faculty of Mechanical Engineering, Universiti Teknologi MARA (UiTM), Malaysia under the support of Principal Investigator Support Initiative (PSI) no: 600-RMI/DANA 5/3/PSI (119/2013).

REFERENCES

[1] Aji, I.S., S.M. Sapuan, E.S. Zainudin & K. Abdan, 2009. KENAF FIBRES AS REINFORCEMENT FOR POLYMERIC COMPOSITES : A REVIEW, 4(3): 239-248.

[2] Akil, H.M., M.F. Omar, AA.M. Mazuki, S. Safiee, Z.A.M. Ishak & A. Abu Bakar, 2011. Kenaf fiber reinforced composites: A review. Materials & Design, 32(8-9): 4107-4121.

[3] Bakar, N.H., K. Mei Hyie, A.S. Ramlan, M.K. Hassan & A. Jumahat, 2013. Mechanical Properties of Kevlar Reinforcement in Kenaf Composites. Applied Mechanics and Materials, 465-466: 847-851.

[4] Davoodi, M.M., S.M. Sapuan, D. Ahmad, A. Ali, A. Khalina & M. Jonoobi, 2010. Mechanical properties of hybrid kenaf/glass reinforced epoxy composite for passenger car bumper beam. Materials & Design, 31(10): 4927-

[5] Matthews, F.L. & R.D. Rawlings, 2002. Composite materials:Engineering and science.Woodhead Publishing Limited.

[6] Herrera-Franco, P., & A. Valadez-González, 2004. Mechanical properties of continuous natural fibre- reinforced polymer composites. Composites Part A: Applied Science and Manufacturing, 35(3): 339-345.

[7] Jacob, M., S. Thomas, & K.T. Varughese, 2004. Mechanical properties of sisal/oil palm hybrid fiber reinforced natural rubber composites. Composites Science and Technology, 64(7-8): 955-965.

[8] Jumahat, A., C. Soutis, & A. Hodzic, 2010. A Graphical Method Predicting the Compressive Strength of Toughened Unidirectional Composite Laminates. Applied Composite Materials, 18(1): 65-83.

[9] Jumahat, A., C. Soutis, F.R. Jones, A. Hodzic, 2010. Fracture mechanisms and failure analysis of carbon fibre/toughened epoxy composites subjected to compressive loading. Composite Structures, Elsevier, 92(2):

295-305.

[10] Mallick, P.K., 2008. Fiber-reinforced composites (Materials, manufacturing, and design) 3rd edition. Taylor and Francis Group

[11] Nunna, S., P.R. Chandra, S. Shrivastava & A. Jalan, 2012. A review on mechanical behavior of natural fiber based hybrid composites. Journal of Reinforced Plastics and Composites, 31(11): 759-769.

[12] Wambua, P., J. Ivens, & I. Verpoest, 2003. Natural fibres: can they replace glass in fibre reinforced plastics? Composites Science and Technology, 63(9): 1259-1264.

[13] Zhang, J., K. Chaisombat, S. He & C.H. Wang, 2012. Hybrid composite laminates reinforced with

glass/carbon woven fabrics for lightweight load bearing structures. Materials & Design, 36: 75-80.

References

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